A universal linear algebraic model for conformal geometries

Cycles Cross Ratio: an Invitation

“…We introduce a new invariant in Lie sphere geometry [3,Ch. 3;6;16] which is analogous to the cross-ratio of four points in projective [26; 30, § 9.3; 32, App. A] and hyperbolic geometries [2, § 4.4; 27, III.5; 29, § I.5].…”